[E2E] Fix test correctness issue (#5315)
[E2E] Fix test correctness issue (#5315)

Set backend before benchmark.load() to avoid move data between two
backends

Co-authored-by: Jiajia Qin <18ef504dc2f2be7888c61ad30571995bf38d04e0@intel.com>
tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs